Thunderbird only: Thunderbird extension Seek adds advanced search and sort functionality to the open source email client, Thunderbird, through a feature called faceted browsing. As you can see in the screencast above, faceted browsing narrows down emails by a number of conditions, introducing tons of useful ways to slice and dice your inbox to find exactly what you want. Add to that the timeline feature, which looks like a blast along with being useful, and we've got a pretty worthwhile Thunderbird extension here. If you give it a go, let's hear what you think in the comments.